Electromagnetic relay with multiple inverse time relationships



Patented pr. 28, 1953v ELECTROMAGNETIC RELAY WITH MULTI- PLE INVERSETIME RELATIONSHIPS John H. Michael', West Allis, Wis., assignor toAllis-Chalmers Manufacturing Company, Milwaukee, Wis.

Application January 25, 1951, Serial No. 207,746

Claims.

This invention relates to improvements in automatic circuit protectivedevices and more particularly to a new and improved delayed actionovercurrent electromagnetic relay.

The usual type of electromagnetic relay has a characteristic fast actionwhich is not adapted to certain circuit arrangements, such as areinvolved in switchgear circuit breaker practice. These applicationsrequire a relay with a time delayed action. The period of time duringwhich electric equipment can be subjected to abnormal conditions, suchas high currents or short circuit currents, is ordinarily variabledepending upon the character or intensity of such abnormal con ditions.In some cases it is desirable to permit the electric system to remainintact for a period of time that varies with the value of an abnormalcondition. At high values of overload currents or short circuitcurrents, it is desirable that the circuit be interrupted after a timeinterval which is comparatively small but which, nevertheless, insuresfreedom from interruption due to momentary disturbances.

Power distribution systems are frequently protected by a number ofserially connected circuit breakers which operate in a predeterminedsequence. Each serially connected breaker is adjusted to trip at adifferent predetermined interval of time, thereby sequentially isolatingsegments of the electric circuit in accordance with the location of thedisturbance, the length of time the disturbance continues or thecharacter of the disturbance. Heretofore, time delay relays have beenused to sequentially trip serially connected circuit breakers but theserelays have not been capable of accurate settings for such short timeintervals as are desirable for clearing circuit faults with a minimum ofburning of connections and connected apparatus.

`In accordance with the invention claimed, a new and improved delayedaction overcurrent electromagnetic relay is provided for circuit breakeroperation which has a given current time characteristic for currents upto a predetermined value and diierent current time characteristics forcurrents above that predetermined value.

In the preferred embodiments of the invention the magnetic relayembodies an armature which actuates a switch operating rod. The rod isretarded by a pair of suction disks from moving into switch actuatingposition in a time varying inversely of the force exerted on the rod.This force varies with the current traversing the winding of the relayas long as the magnetic circuit of the relay remains unsaturated. Forcurrents (Cl. F-372) below a predetermined value the armature remains inthe position shown adjacent the relay core structure to provide an airgap of a predetermined value, and for currents above a certain value thearmature is actuated to provide one or more positions which define airgaps of smaller values.

In order to accurately calibrate the electromagnetic relays so as totrip a plurality of serially connected circuit breakers, the relay isprovided with means for varying the tension on the springs arrangedbetween the armature and a flange provided on the switch actuating rodwithout varying the size of the original air gap.

It is, therefore, one object of the present invention to provide a newand improved delayed action overcurrent electromagnetic relay in whichthe relay has a given current time characteristic for overload currentsup to a predetermined value and different current time characteristicsfor currents above that predetermined value.

Another object of this invention is to provide a new and improveddelayed action relay which is adjustable for operation at predeterminedcurrent values with predetermined periods of time delay.

A further object of this invention is to provide a new and improveddelayed action magnetic relay with multiple inverse time relationshipswhich provide for adjustments of the point of changeover from onerelationship to the other.

Objects and advantages other than those set forth will be apparent fromthe following description when read in connection with the accompanyingdrawing, in which:

Fig. 1 is a diagrammatic view of a circuit breaker and a delayed actionovercurrent electromagnetic relay therefor embodying the presentinvention;

Fig. 2 is a view in axial cross section through a modified embodiment ofthe armature and controlling structure used therewith illustrated inFig. l;

Fig. 3 is a graph of the current time characteristics of theelectromagnetic relay illustrated in Fig. 1 and a graph of a currenttime characteristic of a relay similar to the one illustrated in Fig. 1but embodying the armature and controiiing structure iiiustrated inr'ig. 2.

Reieiring more particularly to the drawing by characters oi' reierence,Fig. 1 illustrates an electric circuit 6 provided with a circuitinterrupter or breaker l and a time delay overcuirent eiectromagneticrelay 8 for controlling its actuation at predetermined overloads. Therelay comprises a magnetizing winding il connected to one phaseconductor of the electric circuit t. Winding t may be connected inseries with the associated phase conductor, or may be connectedtherewith through a current transformer, as is well known. The relayfurther comprises a core structure li. and an armature li. Armature liis or" cylindrical forni and is provided with a central opening l2 intoone end of which a nut i3 is screwed. The armature is disposed adjacentcore structure it to form therewith a magnetic circuit having a givenair gap.

A core lil extending through the central portion of armature li isthreaded therein, and another core lil is threaded in core l2. Core itis arranged within armature Il and core lll but extends beyond core it.

The armature ii, nut i3, core lli and core lil are provided with alignedopenings loosely receiving a rod it for actuating the circuit breakerswitch arm it. rthe rod i6 is provided with a flange portion i9 enclosedVwithin armature Ill and Ahaving a sliding nt therewith. rllhe lower endof the rod it is threaded into a nut 2Q which is, in turn, suitablysecured to one of a pair of suction disks. Nut may be `pinned to rod leto lock it in piace, if so desired. A resilient means such as a springA2i is arranged within armature il about rod it for opposing movenientof armature l l relative to rod it. Spring 2i is mounted between harigeit and a nut 22. Nut 2E is threaded into armature il land 'may be usedfor adjusting the tension of spring 2l without changing the relativeposition of armature il and core structure il?, thereby retaining thesize of the original air gap. 'Nut 22, further, may be used to lock inposition core lit, and a nut 25, as illustrated, will provide Yadefinite arrangement between cores it and i5.

Another resilient means such as a spring '23 is arranged within armaturell about rod i6 for opposing movement of armature il relative to rod it.Spring 23 is arranged between ilange it on rod it and a -flange 2dlmounted on core Hl.

A rigid cylinder 2l surrounds the` lower `end of armature l l and issuitably secured to core structure it and acts as a guiding means `orbearing for the armature. Flange i9 ci rod l5 acts as a guiding meansfor the upper end of armature i i, and a rigid cylinder 28 suitablysecured to core structure le acts as a guiding means .or bearing `forthe upper portion of rod It and also a stop for armature i l.

The suction disks are arranged inan Oil bath withthe upper disk 2ssecured torod It and the lower disk 3c secured to thefbottom .of a4container Si which houses the oil.

Circuit breaker i as illustrated in the drawing comprises stationaryarcing contacts 32 and movable arcinsr contacts The movable arcingcontacts 33 are connected to a rod 31% which is actuated to circuit open.position Yloy -a toggle mechanism.

The toggle mechanism 35 .comprises a link 36 which is pivotallymounted/atl 3l `and a link 32 which is pivotally. mounted at a point teon rod 34. A spring biases-toggle mechanismt to circuit .open position.Link 36 carries a lug t3 which is engaged by a catch dll. Catch M ismounted .on one end ci pivotally mounted lever arm it and is held in itsoperative position against .a stop i5 by means of a spring lit, Leverarm i8` is actuatedby rod it when the latter is actuated to switchopening position by armature il.

Fig. 2 is an enlarged diagrammatic view of a modification ci' thearmature and controlling structure therefor, illustrated in Fig. l. Byadding a resilient means such as spring ill, acting between a flange i3which forms a part of core i5 and flange i9, the operation cf relay 8may be varied to obtain a series of different time delaycharacteristics.

'n Fig. 3 curve ABC illustrates a time current curve of the usual priorart current responsive relay. The curve ABDE illustrates the timecurrent curve of the `electronriagnetic relay illustrated in Figi, andthe curve ABE-G illustrates a time current curve of a relay of the typeillus- .trated in Fig. -l but `incorporating the armature andcontrolling structure shown in Fig. 2. These curves are plotted withcurrent as abscissas and time as ordinates. All of the curves areplotted on 'the basis of the relay being set for ltripping onlyon'values ci current above 106% load. Fig. 3 illustratesdiagrainmatically the manner in which the relay incorporating thearmatures illustrated in Figs. i and 2 may operate and is not intendedto set any limits within which-this invention must be restricted.

"in operation, the circuit breaker i being closed as indicate-d in Fig.l, current flows through the arci-ng contacts S2, 33 andthe inagnetizingwinding il, For all line currentsbelow Aa certain value the parts oftherelay remain in ytheI position indicated. Upon the occurrence of anoverload line current through magnetizing winding il below apredetermined value, the upward .attraction of armature il isinsufficient to lcompress springs 25, 2S. owever, the springs transmitthe thrust vexerted by the armature to rod i6. liter a predetermineddelay the disks separate and armature ii,springs 2i, 23 androd it moveas a unita-nd actuate arm it to trip vthe circuit breaker i Operation ofthe relay illustrated in Fig. l for overload currents belogwgsuchpredeterminedvalue may be illustrated by curve AB in Fig. 3. This typeof linverse time' delay is characteristic o f the prior art lrelaystructures wherein'the time delay is inversely proportional `to theVcurrent owingthrough the magnetizing winding for the full overloadcurrent range of the relay.

In order to permit thev relay'to `operate 'faster for overload currentsabove a predetermined value `the vrelayV illustrated in Fig. l isprovided with an `armature which, when the current reaches thepredetermined value, .moves relative to the switch'actuating rod it froma rstposition to a second position Whereat the .Spfng 12! and 2S aregradually compressed a predetermined distance depending on the currentintensity. 1n the second position of armature il, the air gap betweenthe armature and the upper part of .core structure is smaller.

The inverse time-relation for a ygiven .relay Setting for Vcurrentsabove the predetermined ,over- `loadvalue is represented by curve BD.Therefore, the relay illustrated in 1 operates for all 'overloadcurrents below a predetermined value on the curve 'AB and for alloverload rcurrei'lts above the predetermined value on thecurve BID.

By providing relay d with threaded cores l and l5 the tensions ofsprings 2i and'tt1 maybe changed without changing the relative positionof armature ll with respect to core structure lil. By varying the`tensions of springs il and 23,`the inversetime relationship of `the`relay inthe medium current range is changed, and the point of'changeover from one relationship to theother has been varied. When theltensions of springs 2i and 23 have been reduced by varying the relative'positions of core i4 and.4 nut 22 with reference to armature il theposition of changeover from curve ABC to curve ABD, namely point B, willhave been moved higher up on the curve ABC, i. e., to a higher timelower current position. Similarly, by increasing the tensions of springsSil and 23 the position of point B of curve ABD be moved to a lowerposition on the curve ABC, i. e., to a higher current lower timeposition. When the line current reaches or exceeds a secondpredetermined value, armature i i moves into engagement with stop 2S. Inthat position of armature Il, springs 2l, 23 transmit to rod it a forcewhich is independent of the value of the line current. In the highcurrent range therefore rod it actuates arm I8 in a constant timeregardless of the value of the line current. The operation of the relayin that range is accordingly represented by a horizontal line DE. Thistype or" operation is desired when the line current exceeds theinterrupting capacity of the circuit brealrer and therefore should beinterrupted by a faster back. up circuit breaker oi higher rating.

Curve ABF@ is the time current curve of relay when the relayincorporates the armature and controlling structure illustrated in Fig.2. By providing spring il? between flange 153 and nange the armature iimust operate during part of its movement against the combined aotions ofsprings 2i, 23 and fil. Spring 4'1 ts loosely into the armature assemblyand is compressed only after armature I l has moved a predetermined.distance in switch actuating direction. Until spring all is compressedthe relay operates as above set forth and as represented by curve ABD.However, when the relay reaches an operating point such as point F oncurve ABD, the upward movement of armature li is arrested by spring di.The energy absorbed by spring 41 in compressing under the upwardmovement of armature Il is stored by spring 47 to be applied towardbreaking the suction oi disks 29 and 361 and toward accelerating rod i6.The operation of the relay in that range is represented by curve FG.

By changing the position of core l5 relative to armature il the distancethat armature li may move before compressing spring 47 may be varied.When the distance of travel of armature Il before compressing hasincreased over that illustrated in the drawing, the point F on curveABFG will be moved lower down on the curve, i. e., to a lower time highcurrent relationship. By decreasing the distance of travel of armatureIl before it starts to compress spring 4l the position of point F willbe moved to a lower current higher time relationship.

The position of point B on curve ABFG may also be varied in a mannersimilar to point B on curve ABD by varying the initial tension onsprings 2l and 23. Thus, a variety of time current relationships may beobtained from the same relay by simply varying the tension on thesprings without varying the relative positions of armature and corestructure.

Although but two embodiments of the present invention have beenillustrated and described, it will be apparent to those skilled in theart that various changes and modications may be made therein withoutdeparting from the spirit of the invention' or from claims.

It is claimed and desired Patent:

to secure by Letters 1. A time delay relay comprising a core strucyture, an armature'disposed adjacent said coreA structure to formtherewith a magnetic circuit having a given air gap, a magnetizingwinding for producing a magnetic flux in said magnetic circuit, anoperating rod having a fiange ar-A nut for opposing movement of saidarmature relative to said rod, and means for varying the position ofsaid nut relative to said cylinder for varying the tension of saidresilient means without changing the length of said air gap.

2. A time delay relay comprising a core structure, an armature disposedadjacent said core .structure to form therewith a magnetic circuithaving a given air gap, a magnetizing winding for producing a magneticiiux in said magnetic circuit, an operating rod having a ange arrangedto be actuated by said armature, means for retarding the movement ofsaid rod into actuated position in a time varying inversely of the valueor the current traversing said winding, said armature comprising acylinder and a nut threaded within said cylinder, said cylinderenclosing said flange, a core threaded in said cylinder for movementtherewith in an adjustable position, a rst resilient means actingbetween said flange and said core for opposing movement of said armaturerelative to said rod, and a second resilient means acting between saidflange and said nut for opposing movement of said armature relative tosaid rod, adjustment of the positions of said core and said nut relativeto said cylinder varying the tensions of said rst and second resilientmeans, respectively, independently of each other and without changingthe length of said air gap.

3. A time delay relay comprising a core structure, an armature disposedadjacent said core structure to form therewith a magnetic circuit havinga given air gap, a magnetizing winding for producing a magnetic iiux insaid magnetic circuit, an operating rod to be actuated by said armature,means for retarding the movement of said rod into actuated position in atime varying inversely of the value of the current traversing saidwinding, resilient means acting between said armature and said rod foropposing movement of said armature relative to said rod from a firstposition to a second position, and a second resilient means actingbetween said armature and said rod for opposing movement of saidarmature relative to said rod from said second position to a thirdposition depending on the value of said current, said armature movingrelative to said rod from said rst position to said second position whenthe current traversing said winding reaches a predetermined value andfrom said second position to said third position when said currentexceeds said predetermined value, said movement of said armaturerelative to said rod varying the inverse time relation between rodactuation and the value of said current.

4. A time delay relay comprising a core structure, an armature disposedadjacent said core the scope of the appended aeeegees,

structure to form therewith a/magrretie circuit having a given air gap,a magnetizing windingior producing a magnetic nuxin said magneticcircuit, an operating rod having a ange arranged to be actuated by saidarmature,izneans for retardine the' movement of said rod intoactuatedpos-ition in a time varying inversely cr" the value oi thecurrent traversingsaid Winding,said armature comprising a cylind r `annia threaded within said cylinder, said` Vcylinder enclosing said ange, acore threaded Within Vsaid cylinder for movement therewithinana'djustabie position, a second core threaded. wit-nin. saidnrst corefor movement therein ein env adjusta'oie position, a it ineens acting;between said; flange and. saidinest coreforonposing movement of saidarmature relative to seid rod, e second resiiient means acting betweensaid iiange said nut for opposing nieve-ment oi said. armature relativetok said i' e, and e third esiiient means arranged between 4seid. Secondcore and said flange ior opposing movement oi saidarmatnre relative tosaid only after said arm-attire hes traveled a predetermined. distance,said armature moving said predetermined distance relative to said rodfrom Ya. first position to a second position when the current traversingsaid winding reaches a predetermined vaiue and :trom said secondposition to a third position depending on the value of said currentwhen. said einrent exceeds said predetermined vaine, said movement ofsaid armatore relative to said rod varying the inverse time relationbetween rod actuation and the vaine ot said current.

5. A time delay relay comprising a core sti'ucture, an armature disposedadjacentsaid core structure to form therewith o, magnetic circuit a. e.having a given air gan, o megnetizing' winding` for producing a magneticfiux in .said magnetic circuit, an operating 'rod having a ange arrangedto be actuated by said armature, means for retarding the movement ofsaid rod into actuated position in a time varying inversely of thevaine' of the current traversing said Winding, a first resilient means:acting between said armature andsaid rod for opposing movement of saidarmaturereietive tosaid rod from 'a first position to a second position,said armature moving` relative to said rod 'from said 'first positionto-said second position when the current traversing said winding;reaches a predetermined valuesaid movement of said armature relative tosaid rod varying the inverse time rLeIat-ion betvveen'rod actuation thevaine of seid current, and 'a second resilient means acting between saidarmature and said rod; for opposingmovement of said armature relative tosaid rod and becoming operativ'eat e point intermediate said rst andsecond positioif-i` thereby varying the inverse .time relationbetweenrod actuation end the value oi said currentt 03N MICHAEL.

References Cited in the le of this patent UNITED STATES PATENTS

